Internet game operators have been ordered to install anti-addiction software on their games to help youngsters stay offline.

The government yesterday issued a regulation, which takes effect on April 15, demanding online operators set up a "game fatigue system" that encourages players under 18 to play less than 3 hours a day.

Online gamers will also be required to register using real names and identity card numbers to indicate if they are younger than 18.

Experts said the move reflects government fears over the social impact of popular online games, which have been blamed for the rising numbers of school children playing truant or even committing crimes.

Under the system, known as the "anti-online game addiction system", the first 3 hours of play for each day is considered "healthy", during which players will be awarded full points in the virtual world. The next 2 hours will yield only half the normal points and there will be no points after 5 hours.

After the 5-hour limit, players will be subjected every 15 minutes to the warning: "You have entered unhealthy game time, please go offline immediately to rest. If you do not, your health will be damaged and your points will be cut to zero."

All the online games run in China, including the Massive Multi-player Online Role Player Games (MMORPG) operated by NASDAQ-listed companies such as Shanda, NetEase and The9 and other games like those run by Tencent, will have to abide by the rule.

According to the regulators' timetable, online game operators will have up to four months to install the system; and games not embedded with the software by July 16 will be shut down.

Zhao Yurun, a spokesman for The9 that runs World of Warcraft in China, said yesterday the system will not have a great impact on the company since a majority of its players are adults.

Other companies, including Shanda and NetEase, also said the impact will be limited.

Last year, there were 31.12 million online game players in China. Of them, about 10 percent were below 18, said Kou Xiaowei, deputy director of the audio-visual and Internet publication department of the General Administration of Press and Publication, one of the eight government departments that released the regulation.

Although online game operators do not regard the system as a drain on revenue, experts said it was the real-name registration policy that may pose a real threat to game operators.

"The system requires every online player to register with their real identity. This will scare away many adult and young users," said Liu Bin, chief analyst at research house BDA China.

Official statistics show that the number of Internet users in China reached 123 million in mid-2006. About 15 percent - or 18 million - were under the age of 18.